Creating fractures in a formation using electromagnetic signals

ABSTRACT

An example system includes a generator to generate electromagnetic (EM) signals, and a rotational device having multiple sides. The rotational device includes an antenna to direct the EM signals to a formation to increase a temperature of the formation from a first temperature to a second temperature. The antenna is on a first side of the multiple sides. A purging system is configured to apply a cooling agent to the formation to cause the temperature of the formation to decrease from the second temperature to a third temperature thereby creating fractures in the formation. The purging system is on a second side of the multiple sides.

TECHNICAL FIELD

This specification relates generally to creating fractures in aformation using electromagnetic signals.

BACKGROUND

During formation of a well a drill bores through earth, rock, and othermaterials to form a wellbore. The resulting wellbore may extend to, orthrough, a subterranean formation (or simply, “formation”) that containshydrocarbon embedded in the formation. Fractures or cracks may beproduced in the formation to allow the hydrocarbon to be extracted. Insome cases, the fractures or cracks may be generated by subjecting theformation to a sudden temperature change. This sudden temperature changemay cause thermal shocks, which occur when a thermal gradient causesdifferent parts of the formation to expand by different amounts. Thethermal shocks in the formation produce the fractures or cracks, andallow the hydrocarbon to flow from the formation into the wellbore ofthe well.

SUMMARY

An example system includes a generator to generate electromagnetic (EM)signals and a rotational device having multiple sides. The rotationaldevice includes an antenna to direct the EM signals to a formation toincrease a temperature of the formation from a first temperature to asecond temperature. The antenna is on a first side of the multiplesides. A purging system is configured to apply a cooling agent to theformation to cause the temperature of the formation to decrease from thesecond temperature to a third temperature, thereby creating fractures inthe formation. The purging system is on a second side of the multiplesides. The example system may include one or more of the followingfeatures, either alone or in combination.

The first side and the second side may face in different directions. Thefirst side and the second side may face in opposite directions.

The example system may include an enabler that is susceptible to heatingby the EM signals to support the temperature of the formation increasingfrom the first temperature to the second temperature. The rotationaldevice may be configured to operate within a wellbore. The EM signalsmay include at least one of microwaves (MWs) or radio frequency (RF)waves.

The example system may include a detector to detect sounds in theformation, and a recorder to record information representing the sounds.The example system may include one or more cleaning nozzles configuredto dispense a cleaning agent to release hydrocarbons from the fractures,and to control a flow of the hydrocarbons out of the fractures. Theexample system may include a casing to protect at least the antenna andthe enabler from physical damage.

The detector may include a transducer, or a geophone, or both atransducer and a geophone. The transducer may be used to monitor soundsfrom the created fractures. The geophone may be used to monitor groundmovement from the created fractures. The generator may be a surface unitlocated on a surface of a wellbore. A guided antenna may be used todeliver the EM signals into the wellbore. The generator may be adownhole unit located inside a wellbore.

The enabler may include ceramics, activated carbon, or a combination ofceramics and activated carbon. The enabler may be located in proximityto the antenna. The enabler and the antenna may be on a first side ofthe multiple sides of the rotational device. The enabler may be outsidethe rotational device and injected into the formation. The enabler maybe a powder, or a slurry, or a putty, or a combination of a powder and aslurry, or a combination of a slurry and a putty, or a combination of apowder and a putty, or a combination of a powder, a slurry and a putty.In some examples, a slurry includes a substance that is a semi-liquidmixture containing small particles suspend in water. In some examples, aputty includes a substance that is a soft, malleable paste.

The rotational device may be configured to rotate and to perform anumber of heating and cooling cycles. Heating may occur from the firstside of the multiple sides and cooling occurring may occur from thesecond side of the multiple sides.

An example method of creating fractures in a formation includesgenerating EM signals and directing, via an antenna, the EM signalsthrough an enabler. The enabler may be susceptible to heating by the EMsignals. The EM signals cause a temperature of a formation to increasefrom a first temperature to a second temperature. The antenna may be ona first side of multiple sides of a rotational device. The examplemethod includes applying, via a purging system, a cooling agent to theformation to cause the temperature of the formation to decrease from thesecond temperature to a third temperature, thereby creating fractures inthe formation. The purging system may be on a second side of multiplesides of the rotational device. The second side may be different thanthe first side. The example system may include one or more of thefollowing features, either alone or in combination.

The example method may include monitoring sound signals in the formationand recording the sound signals. The example may include producing theEM signals using a generator. The EM signals may be produced on asurface of a wellbore. The EM signals may be produced inside a wellbore.

The enabler may be injected into the formation in a powder form to fillformation pores. The enabler may be filled into a mini-fracture createdalong the circumference of a wellbore. The mini-fracture may be createdusing a laser.

The first temperature may be a formation temperature. The formationtemperature may depend on the type of reservoir. For example, theformation temperature of an oil reservoir may be 120° F. (48.8° C.) to180° F. (82.2° C.). In another example, the formation temperature of agas reservoir may be 270° F. (132.2° C.) to 320° F. (160° C.). Thesecond temperature may be greater than 1,000° C. The second temperaturemay be less than 1,000° C. The temperature of the formation may increasefrom the first temperature to the second temperature in 10 to 30minutes.

Advantages of the example systems and processes described in thisspecification may include one or more of the following. The systems andprocesses may use limited water to generate fractures and cracks in theformation of the wellbore. As such, the example systems and processesmay provide a relatively clean and environmentally-friendly technologythat may not damage the formation significantly. Furthermore, theexample systems and processes may reduce the consumption of chemicalsassociated with fracturing, which may reduce the cost and environmentalimpact of fracturing.

Any two or more of the features described in this specification,including in this summary section, may be combined to formimplementations not specifically described in this specification.

At least part of the methods, systems, and apparatus described in thisspecification may be controlled by executing, on one or more processingdevices, instructions that are stored on one or more non-transitorymachine-readable storage media. Examples of non-transitorymachine-readable storage media include read-only memory, an optical diskdrive, memory disk drive, random access memory, and the like. At leastpart of the methods, systems, and apparatus described in thisspecification may be controlled using a computing system comprised ofone or more processing devices and memory storing instructions that areexecutable by the one or more processing devices to perform variouscontrol operations.

The details of one or more implementations are set forth in theaccompanying drawings and the description subsequently. Other featuresand advantages will be apparent from the description and drawings, andfrom the claims.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an example system for changing thetemperature of a formation to stimulate fracturing or cracking in theformation.

FIG. 2 is a cross-section of an example wellbore containing an exampleof the system having a downhole-generator unit.

FIG. 3 is a cross-section of an example wellbore containing an exampleof the system having a surface-generator unit.

FIG. 4 is a flowchart showing an example process for changing thetemperature of a formation using electromagnetic (EM) signals.

Like reference numerals in different figures indicate like elements.

DETAILED DESCRIPTION

Described in this specification are example systems for producingfractures or cracks in a formation (referred to as “fracturing”) usingelectromagnetic (EM) signals. Examples of EM signals that can be usedinclude, but are not limited to, microwaves, radio frequency (RF)signals, infrared (IR) signals, ultraviolet (UV) signals, and X-rays.The EM signals are applied to a formation to generate heat in theformation, and are applied using a tool, examples of which are describedin this specification. The EM signals heat the formation to atemperature greater than an ambient temperature of the formation, calledthe “formation temperature”. The formation temperature may depend on thetype of reservoir. For example, the formation temperature of an oilreservoir may be 120° F. (48.8° C.) to 180° F. (82.2° C.). In anotherexample, the formation temperature of a gas reservoir may be 270° F.(132.2° C.) to 320° F. (160° C.). Following heating, the parts of theformation that were heated are then cooled using a cooling agent, alsoapplied by the tool. The heating, followed by relatively rapid cooling,causes expansion and contraction in the formation that produces thefractures or cracks, which allow hydrocarbons to be extracted from theformation. Example components of the tool are described subsequently.The tool, however, is not limited to these components, or to thecombination of components.

In the examples described in this specification, the tool is used afterdrilling the wellbore. The tool is lowered into the wellbore proximateto the formation that is to be subjected to fracturing. For example, thetool may be lowered from a wellhead into the wellbore using anyappropriate technologies. In an example, the tool is multi-sided androtatable within the wellbore. In an example, a first side of the toolcontains one or more EM generators and one or more EM antennas, whichare configured to produce, and to direct, EM signals to toward theformation. The EM signals are applied at an appropriate intensity, andfor an appropriate duration, to heat part of the formation to at least apredefined target temperature. For example, the predefined targettemperature may be at least 1,000° C., or at least 1,100° C., or atleast 1,200° C., or at least 1,300° C., or at least 1,400° C., or atleast 1,500° C. A second side of the tool contains one or more purgingnozzles configured to provide a cooling agent to the part of theformation that was heated by the EM signals.

In an example, the one or more EM generators and the one or more EMantennas together constitute an EM source. In operation, the EM sourceis arranged to face the part of the formation to be subjected tofracturing. The EM source is activated for an appropriate period of timeto apply EM signals to the part of the formation to be heated. Forexample, an appropriate period of time may be at least 30 seconds, or atleast 1 minute, or at least 2 minutes, or at least 3 minutes, or atleast 4 minutes, or at least 5 minutes. The EM signals cause thetemperature of the formation to rise relatively rapidly from theformation temperature—which is the ambient temperature of the formationas described previously—to a target temperature. The magnitude of thetarget temperature may depend on factors such as the size of theformation, and the type of rock or other materials in the formation.

The tool may then be rotated so that the purging nozzles face the partof the formation that was heated by the EM signals. The purging nozzlesoutput cooling agent to the part of the formation that was heated to thetarget temperature in order to cause the temperature of the heated partof the formation to decrease relatively rapidly to a third temperature,also known as the cooling temperature. For example, the rate of changeof temperature may be, but is not limited to, up to 80° C. (Celsius) perminute, or up to 90° C. per minute, or up to 100° C. per minute, or upto 110° C. per minute, or up to 120° C. per minute. The sudden change intemperature causes thermal shocks in the formation that result infractures or cracks in the part of the formation that was heated andthen cooled using the tool. These fractures or cracks facilitateextraction of hydrocarbon from the formation using appropriatetechnologies.

In an example operation, the tool is configured to heat the formation,and then to cool the formation, multiple times in succession. Theheating and cooling may be achieved by repeatedly rotating the toolwithin the wellbore so that the EM source is first exposed to the partof the formation to be fractured, and then the purging system is exposedto the part of the formation that was exposed to the EM source, and soforth. For example, the tool can be used to heat the formation in thewellbore using EM signals and to cool the formation in the wellboreusing the cooling agent at least 10 times, or at least 20 times, or atleast 30 times, or at least 40 times, or at least 50 times, or at least60 times, or at least at least 70 times, or at least 80 times, or atleast 90 times, or at least 100 times. The multiple cycles of heatingand cooling of the formation—referred to as thermal cycling—result infurther propagation of fractures or cracks formed in the part of theformation. For example, the rate of propagation of fractures and cracksin the part of the formation that was heated and cooled using the tool,may depend on, but is not limited to, factors such as the size of theformation, the type of rock or other materials in the formation, themagnitude of target temperature, the number of thermal cycles, or therate of change of temperature.

In some implementations, such as that shown in FIG. 1, the tool includesEM generator 1 to generate EM signals 5; EM enabler 2 that issusceptible to heating by the EM signals to cause a temperature offormation 6 to increase from a formation temperature to a targettemperature; and rotational motor 3 having multiple sides. Rotation ofrotational motor 3 having multiple sides is represented by arrow 16. Forexample, the rotational motor may have, two sides, or three sides, orfour sides, or five sides. In some implementations, for example, themultiple sides can face in different directions. In someimplementations, for example, the multiple sides can face in oppositedirections.

In the example of FIG. 1 the rotational motor has two sides. In someimplementations, for example, the rotational motor includes EM antenna 4to output EM signals 5 to formation 6 to cause a temperature of theformation to increase from the formation temperature to the targettemperature. In an example, the EM antenna may be on a one side of themultiple sides. In some implementations, EM generator 1 feeds power toEM antenna 4 through power cable 9. The rotational motor also includes apurging system. In this example, the purging system includes purgingnozzles 7 to apply cooling agent 8 to the formation to cause thetemperature of the formation to decrease from the target temperature toa cooling temperature that is closer to a temperature of the coolingagent used in order to create fractures in the formation. The purgingsystem may be on a different side of the rotational motor than the EMantenna. In some implementations, the purging system and the EM antennaare on opposite sides of the rotational motor; however, this is not arequirement of the tool.

In some implementations, such as that shown in FIG. 1, the tool includesprotective casing 10 to encase in whole, or in part, at least the EMgenerator, the EM antenna, and the EM enabler. The casing may beconfigured, arranged, or configured and arranged to protect the EMgenerator, the EM antenna, and the EM enabler from physical damage, orchemical damage, or physical and chemical damage, or other environmentalor operational dangers.

As explained previously, the formation temperature may depend onmultiple factors including the size of the formation, the type of rockor other materials in the formation, and ambient pressure in theformation. Furthermore, the magnitude of the target temperature, asdiscussed previously, may depend on factors such as the size of theformation, and the type of rock or other materials in the formation. Forexample, the target temperature may be at least 900° C., or at least950° C., or at least 1,000° C., or at least 1,050° C., or at least1,100° C., or at least 1,200° C., or at least 1,300° C., or at least1,400° C., or at least 1,500° C. The cooling temperature may depend onvarious factors, including but not limited to, the type of cooling agentused, and the amount of cooling agent sprayed on the formation. Forexample, the cooling temperature may be the formation temperature. Inanother example, the cooling temperature may be at least 50° C., or atleast 100° C., or at least 150° C., at least 200° C., or at least 250°C., or at least 300° C., or at least 350° C., or at least 400° C., or atleast 450° C., or at least 500° C., or at least 550° C., or at least600° C. The target and cooling temperatures may also be dictated by thesize and extent of fractures or cracks to be formed. For example, if thefractures or cracks are to be large and extensive, the temperaturedifferential between the target and cooling temperatures may be largerthan in cases where the fractures or cracks are to be less large, lessextensive, or both.

Referring to FIG. 2, in an example implementation, EM generator 1 and EMantenna 4 is located on the rotational tool and are used to generate EMsignals 5 downhole in the wellbore. EM generator 1 and EM antenna 4 maybe fed power by power cable 9 from the surface of wellbore 15 nearwellhead 12 to provide electrical energy needed to generate EM signalsto heat the formation in the wellbore. In this example, the EM signalsare directed by EM generator 1 and EM antenna 4 to formation 6 in thewellbore that the EM generator and EM antenna faces.

In some implementations, as shown in FIG. 3, EM generator 1 is locatedon the surface of wellbore 15, near to the wellhead. The EM signals aredelivered through the wellbore using various technologies. For example,the EM signals can be delivered to the rotational motor using EM guidedantenna 17. Then, EM antenna 4 located on one side of rotational motor 3directs the EM signals through the EM enabler (not shown in FIGS. 2 and3) to formation 6 to increase the temperature of the formation from theformation temperature to the target temperature.

In some implementations, for example, an EM enabler is located alongsideEM antenna 4 on rotational motor 3 of the rotational tool. In anexample, the EM enabler is located in close proximity to the EM antenna,and is configured as an EM enabler plate to be placed against the EMantenna. EM signals generated by the EM generator are then, for example,directed by the EM antenna through the EM enabler plate, thereby heatingthe EM enabler and generating high-energy EM signals. These high-energyEM signals contact formation 6 and increase the temperature of theformation from the formation temperature to the target temperature.

In some implementations, for example, the EM enabler is not locatedalongside EM antenna 4 on rotational motor 3 of the rotational tool, butis located on formation 6 or in the formation. Examples of types of EMenabler that may be used with the tool include, but are not limited to,a powder, a slurry, or a putty. In some examples, a slurry includes asubstance that is a semi-liquid mixture containing small particlessuspend in water. In some examples, a putty includes a substance that isa soft, malleable paste. For example, the EM enabler in powdered formmay be dispersed in the formation, on the formation, or both in theformation and on the formation to fill pores of the formation around thewellbore. The EM signals generated by the generator are then, forexample, directed by the EM antenna on or into the formation, causingthe EM enabler powder in the pores of the formation to heat-up from theambient or formation temperature to the target temperature. Generatedheat 11 (shown as arrows in FIGS. 2 and 3) from the EM enabler at thetarget temperature contacts the formation and increases the temperatureof the formation from the ambient or formation temperature to the targettemperature.

As noted, in some implementations, the EM enabler is in the form of aslurry, or a putty. In an example, a mini-fracture may be created alonga circumference of the wellbore using various technologies. For examplethe width of a mini-fracture is generally in millimeters. For example, amini-fracture may have, but is not limited to, a width of 0.1 millimeter(mm), 0.2 mm, or 0.3 mm. However, regular fractures or cracks arelarger. For example, regular fractures may have, but is not limited to,a width of greater than 0.5 mm. For example, a regular fracture or crackmay have a width of 0.5 mm, 0.6 mm, or 1 mm. The surface length of anexample mini-fracture created along the circumference of the wellborewall using various technologies may be around a few centimeters.Examples of mini-fracture-creating technologies that are usable with thetool may include, but are not limited to, a laser, or a drill. The EMenabler is filled into the mini-fracture. The EM signals generated by EMgenerator are then, for example, directed by EM antenna 4 to theformation, causing the EM enabler in the mini-fracture to heat-up fromthe initial formation temperature to the target temperature or to atemperature that is within an acceptable tolerance of the targettemperature.

The EM enabler can be made from any appropriate materials. In someimplementations, for example, the EM enabler is a ceramic, an activatedcarbon, or a combination of a ceramic and an activated carbon. In someexamples, these materials can heat-up to relatively high targettemperatures, for example around 1000° C., when exposed to EM signals.The target temperature, as discussed previously, may depend on, but isnot limited to, the EM enabler used, the form of the EM enabler, thesize of the formation, and the type of rock or other materials in theformation. Examples of target temperature include, but are not limitedto, 900° C., 950° C., 1000° C., 1050° C., and 1100° C. The rate ofchange of temperature may depend on multiple factors. For example, thechoice of EM enabler material may affect the rate of change oftemperature. The rate of change of temperature may also depend on otherfactors, such as the intensity of the EM signal applied, and thematerials in the formation.

In some implementations, an example purging system includes one or morenozzles on a side of rotational motor 3 that is different from—forexample, opposite to—the side of the rotational motor containing the EMantenna 4. For example, the purging system may include two, three, four,or any appropriate number of nozzles. The nozzles of the purging systemcan be arranged in different configurations. For example, the nozzlesmay be arranged vertically, horizontally, in a grid, or in any otherpattern. In an example, referring to FIGS. 2 and 3, the nozzles 7 of thepurging system are arranged vertically, one on top of the other,parallel to the longitudinal dimension of the tool. In another example,the nozzles can be arranged horizontally such that they areperpendicular to the longitudinal dimension of the tool. In anotherexample, the nozzles can be arranged in a grid having a number of rowsand columns.

The purging system is configured to spray, direct, or otherwise output acooling agent onto the formation that has been heated from the formationtemperature to the target temperature. Application of the cooling agentdecreases the temperature of the heated formation from the targettemperature to the cooling temperature, which is a temperature that iscloser to the temperature of the cooling agent. For example, referringto FIGS. 2 and 3, the one or more nozzles 7 on the other side of the ofthe rotational motor sprays cooling agent 8 to cool the formation fromthe target temperature to the cooling temperature closer to temperatureof the cooling agent. The cooling agent may be in the form of, but isnot limited to, a gas, a liquid, and a fluid. The cooling temperature,as mentioned previously, may depend on multiple factors, including butnot limited to the type of cooling agent used, and the amount of coolingagent sprayed on the formation. The type of cooling agent used duringthe fracturing process may also depend on various parameters, including,but not limited to, the target temperature to be achieved, the rate oftemperature decrease desired, and the type of rock or other materials inthe formation. Examples of cooling agents may include, but are notlimited to, one or more of the following: air, nitrogen gas, inertgases, or water. The amount of cooling agent used to attain the coolingtemperature may depend on a number of factors. These may include, forexample, the type of cooling agent used, the cooling temperaturedesired, the type of rock or other materials in the formation, or theamount of fracturing to be achieved.

In some implementations, the rotational tool includes detector 13 formonitoring a stimulation of the formation to be fractured. For example,the detector may be configured, arranged, or configured and arranged tomonitor sounds from generated fractures and cracks in the formation.Examples of the detector may include, but are not limited to, a detectorhaving acoustic detection capabilities, geophones, or transducers. In anexample, a transducer detects acoustic signals and converts them toelectronic signals. In an example, a geophone detects ground movementand converts it into electronic signals.

In some implementations, referring to FIGS. 2 and 3 for example, thedetector 13 includes at least a transducer that detects acoustic signalsand converts the acoustic signals to electronic signals. In someimplementations, the tool includes multiple transducers. For example,the tool may include two, three, four, or more transducers. In someimplementations, for example, the detector includes at least a geophonethat detects ground movement and converts signals representing theground movement into electronic signals. In some implementations, thetool includes multiple geophones. For example, the tool may include two,three, four, or more geophones. In some implementations, for example,the detector includes at least a transducer and at least a geophone thatmonitor both acoustic signals and ground movement and convert signalsrepresenting sound and ground movement, respectively, into electronicsignals. In some implementations, the tool includes multiple transducersand multiple geophones. For example, the tool may include two, three,four, or more transducers and two, three, four, or more geophones.

In some implementations, a system including the detector also includes arecorder for recording sounds from generated fractures and cracks in theformation that are detected by the detector. The recorder may beconfigured, arranged, or configured and arranged to record electronicsignals that are outputted by the detector. The electronic signals mayinclude or be, for example, voltage, current, radio frequency (RF)signals, or acoustic signals.

The detector and recorder combined may be used, for example, todetermine the success and functionality of the fracturing operation.Indicators of operational success and functionality may include, forexample, but are not limited to, increases in fracture dimensions, andincreases in well productivity. Measurement of these indicators may beperformed using various technologies. In some implementations therecorder may be located in close proximity to the detector. For example,the recorder may be located on the tool. In some implementations, therecorder may be located on the surface of the wellbore near thewellhead. Then, the recorder may be connected to the detector on thetool through wired or wireless technologies. In an example, the recordermay be connected to the downhole detector via a data cable. Therecorder, for example, may also be connected to a downhole detectorlocated on the tool, through various wireless technologies. For example,the recorder may be connected to the detector located on the toolthrough Bluetooth, WIFI, or other appropriate technologies.

In some implementations, the system includes one or more cleaningnozzles to aid in cleaning the fractures generated in the formation. Forexample, the tool may include two, three, four, or more cleaning nozzles14. The cleaning nozzles can be arranged in different configurations.For example, the cleaning nozzles may be arranged vertically,horizontally, in a grid pattern, or in any other pattern. In an example,the cleaning nozzles of the tool are arranged vertically, or one on topof the other, parallel to the longitudinal dimension of the tool. Inanother example, referring to FIGS. 2 and 3, cleaning nozzles 14 can bearranged horizontally such that the nozzles are perpendicular to thelongitudinal dimension of the tool. In another example, the nozzles canbe arranged in a grid having a finite number of rows and columns.

The one or more cleaning nozzles may be configured to spray, direct, orotherwise output a cleaning agent onto the fractures in the formationthat have been generated from repeated heating and cooling of theformation in the wellbore. Spraying of the cleaning agent onto thefractures in the formation may aid in cleaning the fractures andremoving debris from the wellbore. Debris in the wellbore may include,for example, fractured rock fragments, mud, and plant roots. Removal ofdebris from the formation may facilitate, for example, furtherfracturing of the formation in the wellbore, and extraction ofhydrocarbons. Spraying of the cleaning agent on to the fractures in theformation may facilitate removal of hydrocarbons produced from thefractures in the formation of the wellbore, and control of the flow ofhydrocarbons out of the fractures. For example, non-removal of debrisfrom the generated fractures may result in the debris such as rockfragments, remaining fracturing fluids, and mud, to plug the generatedfractures, thereby preventing the flow of hydrocarbons.

In an example, referring to FIGS. 2 and 3, the one or more cleaningnozzles 14 are located on top of the rotational motor. The cleaningnozzles may be located in other locations of the tool. For example, thecleaning nozzles may be located downhole, to the side, or elsewhererelative to the rotational motor. The cleaning agent may include, but isnot limited to, a gas, a liquid, or a fluid. The type of cleaning agentused during the fracturing process may depend on various parameters,including but not limited to, the depth of wellbore and the amount offracturing of the formation the type of rock or other materials in theformation. The cleaning agent may include, but is not limited to, one ormore of the following: air, nitrogen gas, inert gases, or water. Theamount of cleaning agent used depends on a number of factors. Thesefactors may include the type of cleaning agent used, the type of rock orother materials in the formation, and the amount of fracturing.

In some implementations, the tool includes a casing to protect the toolfrom environmental or operational dangers. Referring to FIGS. 2 and 3,for example, casing 10 is used to encase, in whole or in part, at leastthe EM generator, the EM antenna, and the EM enabler. The casing may beconfigured, arranged, or configured and arranged to protect the EMgenerator, the EM antenna, and the EM enabler from physical orelectromagnetic damage. In some implementations, the casing can be usedto encase and, therefore, to protect additional components of the tool.These additional components may include, but are not limited to, the oneor more detectors located on the tool, the one or more recorders locatedon the tool, and additional wireless or wired technologies located onthe tool.

The threat of physical damage to components of the tool may be due toelements contained in the formation or components that are part of thetool itself. Examples of elements of the formation that can causephysical damage to the tool include, but are not limited to, debrisgenerated in the formation due to fracturing of the formation in thewellbore, or hydrocarbons in the formation generated from fractures inthe formation in the wellbore. Examples of components of the tool thatcan cause physical damage to the tool include, but are not limited to,the cooling agent, or the cleaning agent.

In some implementations, for example, the casing is made of a materialthat is transparent to EM signals generated and transmitted by theencased EM generator and EM antenna. In some implementations, forexample, the casing is made of a material that is transparent to boththe EM signals and the heat generated and transmitted by the encased EMgenerator, EM antenna, and EM enabler. Examples of materials used in thecasing include, but are not limited to, plastic, glass, or stainlesssteel. The material used to make the casing may be selected for itsstrength and its ability to handle extreme heat—for example up to thetarget temperature—and a rapid rate of change in temperature in thewellbore during the operation of the tool. In some implementations, thecasing may be a pipe. For example, the pipe may have a circularcross-section, or a rectangular cross-section, or an ovoidcross-section. The dimensions of the pipe, for example, length,thickness, and diameter, may depend on various factors including, butnot limited to, the type of wellbore, the depth of the wellbore, or theproduction capacity of the wellbore. For example, the thickness of thepipe may be at least 0.15 inches, or 0.25 inches, or at least 0.35inches, or at least 0.5 inches, or at least 0.6 inches, or at least 0.75inches, or at least 0.8 inches, or at least 1 inch. In someimplementations, for example, a diameter of a circular cross-sectionalpipe casing may include, but is not limited to, at least four inches, orat least five inches, or at least six inches, or at least seven inches,or at least eight inches, or at least nine inches, or at least teninches.

The time needed to heat and to generate fractures in a formation of awellbore may vary based on a number of conditions. These may include,but are not limited to, the formation temperature, the targettemperature, the cooling agent used, the intensity of the EM signal, thetype of rock or other materials in the formation, the electricproperties of the formation, and the EM enabler. For example, it maytake five minutes, ten minutes, twenty minutes, or thirty minutes, ormore, for the tool to stimulate thermal shocks in the formation by rapidheating and cooling of the formation in the wellbore. The tool, however,is not limited to these durations.

The number of generated fractures in the formation of the wellbore maybe different for different formations. For example, the rate of fracturegeneration may depend on various factors. These include, but are notlimited to, the type of rock or other materials in the formation, thenumber of thermal cycles, the cooling agent used, and the intensity ofthe EM signals applied. In some implementations, generating fractures inthe formation of a wellbore may include generating smaller superficialfractures on a surface of the formation in the wellbore. In someimplementations, generating fractures in the formation of a wellbore mayinclude generating large deep fractures in the interior of theformation. The depth of a fracture generated by the tool may depend onmultiple factors including, but not limited to, the type of rock orother materials in the formation, the number of thermal cycles, thecooling agent used, and the intensity of the EM signals applied.

Referring to FIG. 4, a process 30 is shown for heating and stimulatingfractures in a formation of a wellbore, and for producing at least partof a well using the techniques described previously. Operation 31includes identifying a reservoir to be fractured. Operation 32 includeslowering the rotational motor of the tool into the wellbore. Examples ofthe tool are described throughout this specification. An example of thetool in a wellbore is shown in FIGS. 2 and 3. Operation 33 includesusing one side of the rotational motor in the wellbore to direct EMsignals through an EM enabler to the formation to heat the formation ina wellbore from the formation temperature to the target temperature.Techniques for directing EM energy through an EM enabler to theformation to heat the formation in a wellbore from the formationtemperature to the target temperature are described previously. In thisregard, FIG. 2 shows the rotational motor in a wellbore having adownhole EM generator and antenna. FIG. 3 shows the rotational motor ina wellbore with a surface EM generator 1. As shown in FIGS. 2 and 3, theEM signals generated by the surface or the downhole EM generator unitare directed through an EM enabler to the formation to increase thetemperature of the formation in a wellbore from the formationtemperature to the target temperature.

Operation 34 includes rotating the tool so that the purging system facesthe part of the formation that was heated using the EM signals, andcooling the heated formation by outputting a cooling agent from thepurging system. Techniques for applying, via the purging system, acooling agent to the heated part of the formation are describedpreviously. As shown in FIGS. 2 and 3, the cooling agent is applied tothe heated formation to decrease the temperature of the formation in thewellbore from the target temperature to the cooling temperature,resulting in thermal shocking of the formation in the wellbore.Operation 35 includes repeating, as necessary or desired, the operationsof heating and cooling the formation by rotating the tool in thewellbore to heat and to cool the part of the formation alternately. Theheating and cooling cycles or the thermal cycling is repeated to producerepeated thermal shocks in the formation in the wellbore. The repeatedthermal shocks to the formation in the wellbore result in fractureformation and propagation along at least part of a circumference of thewellbore.

Operation 36 includes removing debris from the wellbore using thecleaning nozzles configured to spray a cleaning agent. As discussedpreviously, one or more cleaning nozzles may spray a cleaning fluid thataid in removal of debris from the wellbore. This may aid, as mentionedpreviously, in the operation for implementing continued, uninterruptedfracturing of the formation in the wellbore. Furthermore, spraying ofthe cleaning agent onto the fractures in the formation may also be usedto facilitate removal of hydrocarbons from the fractures in theformation, and to control the flow of hydrocarbons out of the fracturesin the formation of the wellbore. Operation 37 includes determining ifthermal cycling and, therefore, the thermal shocking of the formation inthe wellbore are to be repeated to achieve a target fracturing of theformation in the wellbore. The success and functionality of thefracturing of the formation in the wellbore is monitored and recorded,as described previously, by the one or more detectors and recorders.After the target fracturing of the formation is achieved, operation 38includes removing the tool from the wellbore.

Although vertical wellbores are shown in the examples presented in thisspecification, the example tools and processes described previously maybe implemented in wellbores that are, in whole or part, non-vertical.For example, the example tools and processes may be performed for afracture that occurs in a deviated wellbore, a horizontal wellbore, or apartially horizontal wellbore, where horizontal is measured relative tothe Earth's surface in some examples.

All or part of the example tools and processes described in thisspecification and their various modifications (subsequently andcollectively referred to as “the processes”) may be controlled at leastin part, by one or more computers using one or more computer programstangibly embodied in one or more information carriers, such as in one ormore non-transitory machine-readable storage media. A computer programcan be written in any form of programming language, including compiledor interpreted languages, and it can be deployed in any form, includingas a stand-alone program or as a module, part, subroutine, or other unitsuitable for use in a computing environment. A computer program can bedeployed to be executed on one computer or on multiple computers at onesite or distributed across multiple sites and interconnected by anetwork.

Actions associated with controlling the processes can be performed byone or more programmable processors executing one or more computerprograms to control all or some of the well formation operationsdescribed previously. All or part of the processes can be controlled byspecial purpose logic circuitry, such as, an FPGA (field programmablegate array), an ASIC (application-specific integrated circuit), or bothan FPGA and an ASIC.

Processors suitable for the execution of a computer program include, byway of example, both general and special purpose microprocessors, andany one or more processors of any kind of digital computer. Generally, aprocessor will receive instructions and data from a read-only storagearea or a random access storage area or both. Elements of a computerinclude one or more processors for executing instructions and one ormore storage area devices for storing instructions and data. Generally,a computer will also include, or be operatively coupled to receive datafrom, or transfer data to, or both, one or more machine-readable storagemedia, such as mass storage devices for storing data, such as magnetic,magneto-optical disks, or optical disks. Non-transitory machine-readablestorage media suitable for embodying computer program instructions anddata include all forms of non-volatile storage area, including by way ofexample, semiconductor storage area devices, such as EPROM (erasableprogrammable read-only memory), EEPROM (electrically erasableprogrammable read-only memory), and flash storage area devices; magneticdisks, such as internal hard disks or removable disks; magneto-opticaldisks; and CD-ROM (compact disc read-only memory) and DVD-ROM (digitalversatile disc read-only memory).

Elements of different implementations described may be combined to formother implementations not specifically set forth previously. Elementsmay be left out of the processes described without adversely affectingtheir operation or the operation of the system in general.

What is claimed is:
 1. A system comprising: a generator to generateelectromagnetic (EM) signals; and a rotational device comprisingmultiple sides, the rotational device comprising: an antenna to directthe EM signals to a formation to increase a temperature of the formationfrom a first temperature to a second temperature, the antenna being on afirst side of the multiple sides; and a purging system to apply acooling agent to the formation to cause the temperature of the formationto decrease from the second temperature to a third temperature, therebycreating fractures in the formation, the purging system being on asecond side of the multiple sides.
 2. The system of claim 1, furthercomprising: an enabler that is susceptible to heating by the EM signalsto support the temperature of the formation increasing from the firsttemperature to the second temperature.
 3. The system of claim 1, wherethe rotational device is configured to operate within a wellbore.
 4. Thesystem of claim 1, where the EM signals comprise at least one ofmicrowaves (MWs) or radio frequency (RF) waves.
 5. The system of claim1, further comprising: a detector to detect sounds in the formation; anda recorder to record information representing the sounds.
 6. The systemof claim 1, further comprising one or more cleaning nozzles configuredto dispense a cleaning agent to release hydrocarbons from the fractures,and to control a flow of the hydrocarbons out of the fractures.
 7. Thesystem of claim 1, further comprising a casing to protect at least theantenna and the enabler from physical damage.
 8. The system of claim 1,where the first side and the second side face in different directions.9. The system of claim 1, where the first side and the second side facein opposite directions.
 10. The system of claim 5, where the detectorcomprises at least a transducer, or at least a geophone, or at least atransducer and at least a geophone.
 11. The system of claim 10, wherethe transducer is configured to monitor the sounds from the createdfractures.
 12. The system of claim 10, where the geophone is configuredto monitor ground movement from the created fractures.
 13. The system ofclaim 1, where the generator comprises a surface unit located on asurface of a wellbore.
 14. The system of claim 13, further comprising aguided antenna to deliver the EM signals into the wellbore.
 15. Thesystem of claim 1, where the generator comprises a downhole unit locatedinside a wellbore.
 16. The system of claim 2, where the enablercomprises ceramics, activated carbon, or a combination of ceramics andactivated carbon.
 17. The system of claim 2, where the enabler islocated in proximity to the antenna, the enabler and the antenna beingon a first side of the multiple sides of the rotational device.
 18. Thesystem of claim 2, where the enabler is outside the rotational deviceand injected into the formation.
 19. The system of claim 18, where theenabler comprises a powder or a slurry or a putty or a combination of apowder and a slurry, or a combination of a slurry and a putty, or acombination of a powder and a putty, or a combination of a powder, aslurry, and a putty.
 20. The system of claim 1, where the rotationaldevice is configured to rotate at a speed and to perform a number ofheating and cooling cycles, heating occurring from the first side of themultiple sides and cooling occurring from the second side of themultiple sides.
 21. A method of creating fractures in a formation, themethod comprising: generating electromagnetic (EM) signals; directing,via an antenna, the EM signals through an enabler, which is susceptibleto heating by the EM signals, to cause a temperature of a formation toincrease from a first temperature to a second temperature, the antennabeing on a first side of multiple sides of a rotational device; andapplying, via a purging system, a cooling agent to the formation tocause the temperature of the formation to decrease from the secondtemperature to a third temperature, thereby creating fractures in theformation, the purging system being on a second side of multiple sidesof the rotational device, the second side being different than the firstside.
 22. The method of claim 21, further comprising: monitoring soundsignals in the formation; and recording the sound signals.
 23. Themethod of claim 21, further comprising producing the EM signals using agenerator.
 24. The method of claim 23, where the EM signals are producedon a surface of a wellbore.
 25. The method of claim 23, where the EMsignals are produced inside a wellbore.
 26. The method of claim 21,where the enabler is injected into the formation in a powder form tofill formation pores.
 27. The method of claim 21, where the enabler isfilled into a mini-fracture created along the circumference of awellbore.
 28. The method of claim 27, where the mini-fracture is createdusing a laser.
 29. The method of claim 21, where the first temperatureis a formation temperature.
 30. The method of claim 21, where the secondtemperature is greater than 1,000° C.
 31. The method of claim 21, wherethe second temperature is less than 1,000° C.
 32. The method of claim21, where the temperature of the formation increases from the firsttemperature to the second temperature in 10 to 30 minutes.